OTSSignsOrchestrator/OTSSignsOrchestrator.Server/Health/Checks/OauthAppAgeHealthCheck.cs

using OTSSignsOrchestrator.Server.Data.Entities;

namespace OTSSignsOrchestrator.Server.Health.Checks;

/// <summary>
/// Checks the age of the OAuth2 application credentials from <see cref="OauthAppRegistry.CreatedAt"/>.
/// Alerts Warning at 180 days, Critical at 365 days. AutoRemediate=false — suggests
/// a "rotate-oauth2" job instead.
/// </summary>
public sealed class OauthAppAgeHealthCheck : IHealthCheck
{
    /// <summary>Days at which severity escalates to Warning.</summary>
    internal const int WarningThresholdDays = 180;

    /// <summary>Days at which severity escalates to Critical.</summary>
    internal const int CriticalThresholdDays = 365;

    public string CheckName => "OauthAppAge";
    public bool AutoRemediate => false;

    public Task<HealthCheckResult> RunAsync(Instance instance, CancellationToken ct)
    {
        var oauthApp = instance.OauthAppRegistries
            .OrderByDescending(o => o.CreatedAt)
            .FirstOrDefault();

        if (oauthApp is null)
            return Task.FromResult(new HealthCheckResult(HealthStatus.Degraded,
                "No OAuth app registered"));

        var ageDays = (DateTime.UtcNow - oauthApp.CreatedAt).TotalDays;

        if (ageDays >= CriticalThresholdDays)
        {
            return Task.FromResult(new HealthCheckResult(HealthStatus.Critical,
                $"OAuth2 credentials are {(int)ageDays} days old (critical threshold: {CriticalThresholdDays}d)",
                "Create a 'rotate-credentials' job to rotate the OAuth2 application"));
        }

        if (ageDays >= WarningThresholdDays)
        {
            return Task.FromResult(new HealthCheckResult(HealthStatus.Degraded,
                $"OAuth2 credentials are {(int)ageDays} days old (warning threshold: {WarningThresholdDays}d)",
                "Schedule credential rotation before they reach 365 days"));
        }

        return Task.FromResult(new HealthCheckResult(HealthStatus.Healthy,
            $"OAuth2 credentials are {(int)ageDays} days old"));
    }
}